404 AGRICULTUEAL AND INDUSTEIAL BACTEBIOLOGY 



gaining entrance into a leaf causes first a localized wilted 

 area, the organisms invade the larger vessels of the fibrovas- 

 cular bundles and the entire leaf wilts. Upon invasion of 

 the main stem the organisms spread rapidly, the vessels are 

 occluded and the entire plant wilts. When the stem is cut 

 the sticky white bacterial mass oozes from the cut bundles, 

 and when touched frequently shows its glutinous character 

 by drawing out in tiny threads. 



Erwinia cabotovoea 



Synonjan. — Bacillus carotovorus. 



This organism causes a soft rot of a considerable number 

 of root crops, particularly carrots and turnips. 



Morphology. — The organism is about .8X2.0ju, motile 

 by means of peritriehous flagella. The other characters 

 are those common to the genus. 



Culture and Physiology. — The organism grows readily 

 upon the usual culture media, generally abundantly to 

 luxuriantly. On agar the growth is smooth, glistening and 

 white. Gelatin is liquefied relatively rapidly. A scum 

 forms in broth. Milk is coagulated and slowly digested. 

 Small amounts of gas and acid are produced in dextrose, 

 lactose and saccharose broth and acid from glycerol. 



Pathogenesis. — This organism usually gains access to 

 the tissues through a wound or injury. It produces an 

 enzyme pectinase capable of dissolving the middle lamella 

 of the cells. The cells then fall apart and are themselves 

 finally invaded and destroyed. The disease is, therefore, a 

 typical soft rot. 



Erwinia melonis 



Synonym.. — Bacillus melonis. 

 This is the cause of a soft rot of the fruit of musk- 

 melons. 



